Human platelet transfusion is widely employed in the management of patients with bleeding problems. As routinely conducted in regional blood banks, the method of platelet preservation, transportation and utilization involves a series of general steps which include collecting whole blood from the donor into a blood bag containing anti-coagulant solution. In a second step platelet-rich plasma (PRP) in a volume of about 250 ml is then separated from other blood cells by differential centrifugation. The platelets are concentrated in the PRP by centrifugation. Packed platelets are then separated in 50-60 ml of plasma. The packed platelets are routinely then resuspended by allowing the cells to rest in a blood bag at room temperature. The platelet concentrates then obtained are used for transfusion. For neonates up to there months old or newborns and infants who are in need of platelet concentrations but cannot tolerate 50-60 ml volume of plasma, plaltelets in the concentration normally obtained are further concentrated by centrifugation with excess plasma removed and the platelets then rested and agitated again. The step to further concentrate can take at least two hours to produce approximately 10 ml of highly concentrated platelets.
The platelets can be transported in many ways but generally are transported in plastic blood bags containing platelet concentrates placed in a box for shipping. Agitation is required in the current method of platelet preservation but may not be applied during transportation for short periods of time. When agitation is not used even for short periods, viability may be decreased particularly if transportation is over long distances and takes some time.
Agitation, which keeps platelets in suspension throughout the perservation period, has in the past been used for storage under earth gravity in order to facilitate gas transport to a surrounding atomosphere. Platelets are metabolically active cells which require oxygen to maintain their viability; at the same time, carbon dioxide must be removed from the plasma or fluid medium surrounding the platelets, otherwise the pH of the suspension can fall and injure the platelets. The oxygen and carbon dioxide must diffuse through the plastic wall of the containers. Failure to agitate platelets during storage can lead to a more rapid fall in pH and a reduction in viability. A fall in pH is always associated with poor platelet perservation with a fall below pH 6.0 being destructive of the platlelets or their function after transfusion into an individual. Diffusion of oxygen and carbon dioxide can be facilitated by agitation of the plastic bag. However, agitation-produced damage to platelets can be demonstrated by a variety of tests which assess platelet function. Generally speaking, the more vigorous the agitation, the more platelet destruction. Force which results in increased platelet-platelet or platelet-surface interactions is deliterious to platelets.